Fix incorrect autotokens check on macos (#3316)

* Fix incorrect autotokens check on macos

* Fix clippy

Author: wtdcode

libafl_targets/src/coverage.rs

@@ -56,18 +56,28 @@ pub use __afl_fuzz_len as INPUT_LENGTH_PTR;
 pub use __afl_fuzz_ptr as INPUT_PTR;
 pub use __afl_sharedmem_fuzzing as SHM_FUZZING;
 
+/// Check if we have enabled autotokens
+#[cfg(any(target_os = "linux", target_vendor = "apple"))]
+pub(crate) fn has_autotokens() -> bool {
+    unsafe {
+        !__token_start.is_null()
+            && !__token_stop.is_null()
+            && __token_stop.offset_from(__token_start) != 0
+    }
+}
+
 /// Return Tokens from the compile-time token section
 #[cfg(any(target_os = "linux", target_vendor = "apple"))]
 pub fn autotokens() -> Result<Tokens, Error> {
     // # Safety
     // All values are checked before dereferencing.
 
     unsafe {
-        if __token_start.is_null() || __token_stop.is_null() {
-            Ok(Tokens::default())
-        } else {
+        if has_autotokens() {
             // we can safely unwrap
             Tokens::from_mut_ptrs(__token_start, __token_stop)
+        } else {
+            Ok(Tokens::default())
         }
     }
 }

libafl_targets/src/forkserver.rs

@@ -33,7 +33,10 @@ use crate::cmps::EXTENDED_CMPLOG_MAP_PTR;
 use crate::cmps::{AflppCmpLogMap, CMPLOG_MAP_PTR};
 use crate::coverage::{__afl_map_size, EDGES_MAP_PTR, INPUT_LENGTH_PTR, INPUT_PTR, SHM_FUZZING};
 #[cfg(any(target_os = "linux", target_vendor = "apple"))]
-use crate::coverage::{__token_start, __token_stop};
+use crate::{
+    coverage::{__token_start, __token_stop},
+    has_autotokens,
+};
 
 /// SAFETY:
 ///
@@ -124,6 +127,7 @@ fn map_shared_memory_common<SHM: ShMemProvider>(
     } else {
         map_size_default_fallback
     };
+
     let shmem = shmem_provider.shmem_from_id_and_size(ShMemId::from_string(&id_str), map_size)?;
 
     Ok(shmem_into_raw(shmem))
@@ -413,7 +417,7 @@ fn start_forkserver_internal<P: ForkserverParent>(
     forkserver_parent: &mut P,
 ) -> Result<ForkserverState, Error> {
     #[cfg(any(target_os = "linux", target_vendor = "apple"))]
-    let autotokens_on = unsafe { !__token_start.is_null() && !__token_stop.is_null() };
+    let autotokens_on = has_autotokens();
     let sharedmem_fuzzing = unsafe { SHM_FUZZING == 1 };
 
     // Parent supports testcases via shared map - and the user wants to use it. Tell AFL.